The purpose of the paper is to study the peculiarities of implementation of such textual categories as completeness, connectivity, dialogization in electronic letter. Object of study is electronic correspondence and the subject is the style, structure, syntax of letters. Material of the research includes published letters of the Doctor of Physical and Mathematical Sciences, Professor R. G. Barantsev to colleagues and friends, as well as their response letters. Descriptive method, methods of contextual and communicative-pragmatical analysis are used in the research. Practical application of the research is possible while teaching the syntax and stylistics of Russian language. Conclusion: speech implementation of a number of textual categories in electronic letters has its own characteristics. Such boundary demarcators of the epistolary text as address, signature, etiquette formulas of greeting and farewell are reducing (in whole or in part) if the exchange of messages is frequent, thereby the formal completeness of the text is weakening. The dialogization in electronic correspondence is formed not only by the linguistic means typical for written messages (address, signature, pronouns and verb forms of the 2nd person), but also in other ways, such as direct quotation instead of transmitting someone else's speech as direct or indirect speech, language game as a stylistic device that forms a certain tone of communication. The widespread use of incomplete and one-compound sentences, pronouns that are not related to the antecedent, increases the importance of common apperception base of the participants in communication for understanding the text and continuing the epistolary dialogue. Specifying the subject of speech by pronouns with the absence of its introductory nomination in a letter, sending to previous texts of the correspondence by pronouns and particles, stylistic unity within the chain of letters exchanged between two correspondents are the means that enhance the coherence of the text, extend it beyond a separate letter and transform the exchange of monologue texts into a continuous epistolary discourse.